This invention relates to color photography.
Many images, particularly those of a technical nature, are continuous tone--i.e., black and white images. These images include, for example, black and white photographic images in various technical works, such as medical books and journals. The photographic images are usually derived from photography, sonography and radiography (X-rays) processes and equipment.
The above-discussed images are all of the type known as "gray continuous tone images", varying between black and white at different portions of the image. The analysis of such images requires significant training in order that the information contained in them may be understood and interpreted. Interpretation is recognized as being somewhat subjective, and in many cases, presents substantial difficulties.
It has been recognized that the human eye has relatively poor gray scale performance; that is, the eye cannot discriminate over as wide a range of intensity level as is desirable in order to assist in the interpretation and understanding of continuous tone images. Recognition of the foregoing fact has led to the development of color coded images, which has been accomplished with complex electronic equipment in, for example, certain oscilloscopes which produce images sensed by radar equipment. Other examples of such equipment where color enhancement is achieved of a black and white image through such electronic equipment is in the area of sonography. In these examples, a color is arbitrarily assigned to each small range of magnitude of the received radar pulse or the received ultrasonic pulse echo. The color coding of oscilloscopes is most successful with relatively simple images having few details and slowly varying intensities, if any.
Color photography is widely used and, in the medical and other technical fields, the provision of color photographs of multicolor objects has been effective as data for conveying information for instructional and diagnostic purposes. The provision of full color photographs in printed material, such as text books and scientific journals is, however, substantially more expensive than with black and white photographs. The result is that some such publications are printed in black and white only for purposes of economy, with attendant loss in the information actually conveyed to the reader.